1. Field of the Invention
This invention relates to a system designed to search for a desired scene represented by a moving picture signal. This invention also relates to a system for detecting a change in scenes (a scene change) represented by a moving picture signal. Furthermore, this invention relates to a recording medium which stores a computer-related video-signal processing program.
2. Description of the Related Art
Japanese published unexamined patent application 7-192003 discloses a system designed to search for a desired scene represented by a moving picture signal. In the system of Japanese application 7-192003, each sequence of 1-frame-corresponding segments which represent caption-added pictures is extracted from the moving picture signal. Typical scenes related to the respective extracted sequences can be indicated on a display. The user can search the indicated scenes for a desired scene.
The system of Japanese application 7-192003 implements a process of discriminating caption-added pictures from caption-less pictures. The system of Japanese application 7-192003 uses the assumption that pixels corresponding to edges of caption characters tend to remain at same positions during a given number of successive frames. For every frame, the number of such pixels is detected. When the number of such pixel exceeds a threshold number, it is decided that the related frame represents a caption-added picture. Otherwise, it is decided that the related frame represents a caption-less picture. The result of this decision tends to be adversely affected by noise in the moving picture signal.
According to a known method of detecting a change in scenes (a scene change) represented by a moving picture signal, every frame related to the moving picture signal is divided into a set of blocks having equal sizes. Detection is made as to differences (variations) in luminance or color between equal-position blocks in two successive frames. A given number of smaller differences are selected from among the detected differences. An inter-frame variation is calculated on the basis of the summation of the smaller differences. When the inter-frame variation exceeds a threshold value, it is decided that a scene change occurs between the two successive frames.
Japanese published unexamined patent application 4-111181 discloses a method of detecting a change point in a moving picture. According to the method in Japanese application 4-111181, every frame related to the moving picture is divided into a set of blocks having equal sizes. Color-related feature quantities are calculated for the respective blocks. Calculation is given of differences (variations) in color-related feature quantity between equal-position blocks in two successive frames. Blocks related to differences greater than a threshold value are regarded as effective-change blocks. A correlation coefficient for the last two frames is calculated on the basis of the number of the effective-change blocks. In addition, calculation is made as to the rate of a change between the present correlation coefficient and the immediately preceding correlation coefficient. When the calculated change rate exceeds a prescribed value, it is decided that a change point occurs in the moving picture.